In modern injection systems for internal combustion engines of motor vehicle piezoactuators, which are electrically controlled and cause a corresponding displacement of an valve pin in the respective injection valve depending on the electrical energy stored within them, are used for mechanical actuation of the injection valves, with the stroke of the valve pin being a function of the electrical energy stored in the piezoactuator.
The piezoactuators are usually electrically activated by a pilot control with an overlaid regulation. In such cases the desired electrical energy of the piezoactuator and thereby the desired stroke of the valve pin are predetermined as a target value. The pilot control then determines in accordance with a predetermined pilot control characteristic a corresponding control variable such as for example the pulse duty ratio for a pulse width modulated activation of a final stage. Adaptation of the pilot control characteristic as part of the overlaid regulation is also known from DE 10 2005 010 028 A1 by the characteristic gradient being adjusted within the framework of the regulation.
The disadvantage of the regulation in accordance with DE 10 2005 010 028 A1 is the fact that the modeled pilot control characteristic does not exactly match the real behavior of the system.
With a target value jump this leads to a control deviation initially occurring. This control deviation is actually regulated out by the regulator by the gradient of the pilot characteristic being adapted accordingly. During the adjustment time of the regulator however a dynamic control deviation occurs which is undesired.